Breast cancer treatments can raise heart risks, doctors warn

Heart disease and cancer are the top two leading causes of death in the United States -- and a new paper highlights how these major health concerns can intertwine.

A scientific statement from the American Heart Association, published Thursday in the journal Circulation, warns that breast cancer patients may be at an increased risk of cardiovascular diseases and could benefit from discussing those risks with their doctors.

"For older women, (cardiovascular disease) poses a greater mortality threat than breast cancer itself. This is the first scientific statement from the American Heart Association on CVD and breast cancer," the statement says.

Cardiovascular disease and breast cancer already have several overlapping risk factors, such as age and obesity, and current lifesaving breast cancer treatments could have negative impacts on heart health, according to the statement.

"We are still recommending that patients do get their breast cancer treatment. They should get the best treatment that's necessary for their breast cancer," she said, but patients should try to prevent or reduce those risks to their heart health by maintaining a healthy diet, exercising, and monitoring their blood pressure and cholesterol.

The intersection of cardiovascular disease and breast cancer is nothing new to oncologists, said Dr. Otis Brawley, chief medical and scientific officer and executive vice president of the American Cancer Society, who was not involved in the statement.

"We have taught and seen these problems. The report may bring this problem to the front of mind among emergency medicine and internal medicine doctors who are caring for these women," he said. "Let's give these drugs and treatments to people who need them -- the risk-benefit is more favorable -- and let's do all we can to determine who is unlikely to benefit from the drugs and spare them the risks."

Globally, breast cancer is the top cancer impacting women's health, in both the developed and the developing worlds, according to the World Health Organization.

The new statement noted that radiation and chemotherapies can pose a risk to cardiovascular health.

A study published in the New England Journal of Medicine in 2013 found that exposing the heart to radiation during radiotherapy could increase the rate of heart disease among breast cancer patients later in life.

The study involved 2,168 women who underwent radiotherapy for breast cancer between 1958 and 2001. It showed that the rate of major coronary events among the women increased 7.4% for each additional gray, or unit, in the average radiation dose delivered to the heart.

Women irradiated for cancer of the left breast, near the heart, had higher rates of major coronary events than women irradiated for cancer of the right breast, the study found.

"It is less a problem today than 20 years ago, because we started aiming the beam to miss the heart about 20 years ago, but we occasionally see a woman who had lumpectomy and radiation, and the radiation beam caught part of the heart and a coronary artery," Brawley said. "This can cause isolated coronary artery disease in that portion of the artery."

"Radiation therapy does have that risk of developing coronary artery disease, and it can be several years to a decade or more later," Mehta said.

Yet "one of the well-known treatments to potentially cause heart problems are anthracyclines," she said of chemotherapy drugs. "Anthracyclines have been shown to result in weakening of the heart muscle and heart failure, which can be irreversible. Oncologists and cardiologists are well aware of this and minimize the dosage as possible to reduce the potential of heart failure."

One observational study of 1,263 breast cancer patients in Dundee, Scotland, found that among those who received anthracyclines alone for treatment, 6.7% developed left ventricular systolic dysfunction, a common cause of heart failure. Among those who received a combination of anthracycline and trastuzumab, another chemotherapy drug, 12.5% developed that systolic dysfunction.

So the study, published in the journal Heart in 2016, suggests that a single chemotherapydrug is associated with less damage to the heart compared with combining drugs.

"Adriamycin, or doxorubicin, and trastuzumab, or Herceptin, are the big causes of heart failure," Brawley said.

"Adriamycin-induced congestive heart failure symptoms can show up three to five years after treatment and easily be missed by an internist or ER doctor who does not see a lot of these patients," he said. "Health care is changing such that a cancer patient often does not see an oncologist after completion of therapy."

In general, the impact of both cardiovascular disease and breast cancer among women can be significant, and Mehta hopes the new statement raises this awareness, especially among older women.

"Older breast cancer survivors are more likely to die from other diseases and not breast cancer, and cardiovascular disease is the most frequent cause," she said.

Maintaining a healthy lifestyle and treating cardiovascular risk factors aggressively can help prevent heart attack, stroke and disability, said Kuller, who also has studied cardiovascular disease and breast cancer.

Overall, "one of the great things about the cancer world right now is that there are more and more survivors," Mehta said.

"Oncologists are doing a terrific job of increasing survival rates by advancing the science and improving cancer treatments. This is much better than a few decades ago," she said. "But there are side effects from these cancer treatments, and we're trying to recognize it in the very early phases so that we may be able to mitigate the heart effects and avoid significant heart damage."

Some breast cancer therapies can pose heart risks, the American Heart Association warns